Railroad locomotives are typically powered by diesel-electric systems or by diesel-hydraulic systems. Conventional stand-alone locomotives have output power typically ranging from approximately 300 horsepower (for example, locomotives used in mining and tunneling) to approximately 6,000 horsepower (for example, locomotives for long haul cross-country freight trains).
Railroads are under increasing pressure to reduce emissions and fuel consumption while maintaining high power capability necessary for rapid acceleration and/or high tractive effort as two common examples. One of several responses to these forces has been the development of hybrid locomotives. Donnelly has disclosed the use of a battery-dominant hybrid locomotive in U.S. Pat. No. 6,308,639 which is incorporated herein by reference. Hybrid locomotives can reduce emissions and fuel consumption in many rail situations such as yard switching but they become less effective for medium haul freight or commuter trains.
Donnelly has also disclosed a method and apparatus for controlling power provided to DC traction motors by furnishing an individual chopper circuit for each traction motor in U.S. Pat. No. 6,812,656 which is incorporated herein by reference. Donnelly et al. have disclosed a method of monitoring, synchronizing and optimizing the operation of the locomotive drive train in U.S. patent application Ser. No. 10/649,286.
The present inventor has further disclosed a system for controlling a dynamic and regenerative braking system for a hybrid locomotive which employs a control strategy for orchestrating the flow of power amongst the prime mover, the energy storage system and the regenerative braking system in a U.S. Provisional Patent Application 60/600,330 which is also incorporated herein by reference.
Other strategies to reduce emissions and fuel consumption involve combinations of conventional and hybrid locomotives in a consist. Donnelly et al. have disclosed a method of allocating energy amongst members of a consist in U.S. patent application Ser. No. 11/070,848; and have disclosed a method for monitoring, controlling and/or optimizing the emission profile for a hybrid locomotive or consist of hybrid locomotives in U.S. patent application Ser. No. 11/095,036, all of which are also incorporated herein by reference.
In the search for efficient engine and fuel strategies, many different power plant and power delivery strategies, other than hybrid systems, have been investigated. Some of these strategies have been based on alternative, cleaner burning fuels. An example of an alternate fuel strategy is contained in a report entitled “LNG as a Fuel for Railroads: Assessment of Technology Status and Economics” which is incorporated herein by reference. This reference discusses the use of diesel fuel or LNG in a diesel engine. Another reference entitled “Comparative Economic Assessment of a Natural Gas Fueled Locomotive with On-Board CNG Storage to Diesel and LNG Variants” discusses the use of natural gas as a fuel for diesel or gas turbine engines and is incorporated herein by reference. An alternate fuel strategy usually involves a substantial change in railroad infrastructure, especially in countries where the infrastructure is based on primarily on diesel fuel.
Yet other strategies to reduce emissions and fuel consumption or increase locomotive power have involved dual engine or multiple engine configurations. Often a multi-engine locomotive can be comprised of engines each of which can provide power to separate driving wheel assemblies or separate groups of driving wheel assemblies. In other designs, the AC electrical output of two engine/alternator systems have been synchronized to provide power to an AC bus which, in turn, provides power to all the locomotive's traction motors. Older multi-engine designs have utilized synchronized mechanical transmissions to supply power directly to the driving wheel assemblies.
The present inventor has previously disclosed a booster unit for diesel electric locomotive comprised of a diesel engine and a gas turbine connected via a DC bus to a series of traction motors in Canadian Patent 1,283,472 which is incorporated herein by reference. This invention does not require its engines to be synchronized but has no load control for its traction motors.
Recently, a French Railway Company, VFLI, disclosed a dual-engine locomotive utilizing a common DC bus electrical transmission where the two engines need not be synchronized. The second engine in this design is brought on-line using a simple algorithm. Under this algorithm, when the power output of the first engine exceeds 70% of its rated value, the second engine is brought on-line.
For application to locomotives with two or more engines to reduce emissions and fuel consumption, Donnelly et all have disclosed a versatile multiple engine control strategy in U.S. Provisional Application 60/674,837 and a high-power density engine packaging method in U.S. Provisional Application entitled “Multiple Engine Locomotive Configuration” filed Jun. 20, 2005. These provisional applications are also incorporated herein by reference.
There remains a need for a straightforward locomotive power plant and drive train architecture that can be applied to a variety of traction motor and drive train configurations known to the rail industry to reduce emissions and fuel consumption and/or increase locomotive power by allowing for (1) the use of various prime movers, (2) the use of various fuels, (3) addition of an energy storage system for propulsion power assist or full propulsion and (4) a regenerative braking system.